It is inevitable that as you grow older that you will realize that the death of friends and relatives is something that is going to happen. Life is tough and will lead you into many low spots. It also has just as many if not more high points. For every death of a loved one, you can find a new life brought into this world that you can choose to love just as much as you did the departed. At your age, you have reached the point where you need to decide how you will react to this inevitability. Many people find strength in religion, while others simply choose some other way to get through it. What you decide is completely up to you. How you face these tests, whether you choose to dwell on the low spots or celebrate the high points will in large part determine the quality of your own life.
Grief is a natural response to the loss of someone you cared about. It may not make sense now, but I've known for years that the person who goes through this process of grief the most, usually does so because they had the ability to attract the most friends and loved ones. These are the type of people who leave the biggest hole when they pass from this world.
Even here in this internet family, we have the perfect example of that in our loss of Jack "Fish for Dollars" Yates a little less than a year ago. The reason we have a dedicated thread in his memory is due to the fact that he opened himself up to all of us so much. While I was never lucky enough to have met the man in person, his life touched mine, and felt the twinge of loss when I heard about his passing. Seeing that thread title doesn't give me nearly as much grief as it gives me pause to remember all of the great things this man meant to so many of us.
And now we come to this point. A friend named Austin who comes here to ask the question why. To look for help in getting through a low spot that he hasn't had to face very often. I can tell you that almost everyone who reads your post will feel a twinge of grief as well, simply by knowing that a friend is facing trouble dealing with this tough life. Many of us will post some sage piece of advice to try to help, and many others will only say a quiet prayer that you find the strength to get through this rough patch. Some like myself will do both.
So my young friend, I will pray that you find the ability to accept this loss, and will find a way to celebrate all of the good times you had with the person you've lost. You learned to care for this person because you shared many of the high points in life, and that caring will continue if you can keep those thoughts alive.